When bathing a baby, run cold water first and then add hot, and test it with the inside of your wrist or your elbow before putting the baby in; if your water heater lets you set the output temperature, set it below 50 ℃

Cost

Free. Testing the water adds a minute or two to each bath. For more certainty, you can buy a water thermometer. The hard part is testing first even when the baby is crying and you are in a hurry.

What you get

The U.S. Consumer Product Safety Commission says most adults get a third-degree burn from touching water at 150 ℉ (about 65 ℃) for 2 seconds. Water at 140 ℉ (60 ℃) for 6 seconds, or at 130 ℉ (about 54 ℃) for 30 seconds, also scalds. Even at 120 ℉ (49 ℃), soaking for 5 minutes can cause a third-degree burn. A WHO report says the skin of infants and young children is thinner than adults', so a lower temperature can scald them, and the burn is deeper. The American Academy of Pediatrics tells parents to test the water in the tub with the inside of the wrist or the elbow, and it should be "warm, not hot." "Never bathe a baby under running water," because the temperature of water moving through pipes goes up and down, and a small change can scald. In 1983 the U.S. state of Washington passed a law that new water heaters must leave the factory preset to 49 ℃. By 1988, the average temperature of hot water in homes had fallen from 61 ℃ in 1977 to 50 ℃. Hospital admissions of children for tap-water scalds fell from 5.5 a year in the 1970s to 2.4 a year. The burned area, skin grafts, deaths and days in hospital were also lower. This is a before-and-after comparison, not a trial with groups. Australia sets a maximum of 50 ℃ for hot taps in bathrooms. In New South Wales from 1989 to 1996, the rate of hospital admissions for scalds among children aged 0 to 4 fell by 13%. For severe scalds with 10 or more days in hospital, the fall was 30% in the two years after the second phase. In three Chinese statistics on hospitalized children with burns, those scalded by hot liquids were 87.6% to 90.6%, and children under 3 were the largest group

Notes

Rated B because the figures come from before-and-after comparisons and hospital record statistics, with no randomized trials. The size of the benefit is set at medium by judgment, because no separate figure for bath-water scalds in China was found. There are two kinds of water heaters. For instant types like gas water heaters, set the output temperature below 50 ℃ directly. Storage electric water heaters are different: the WHO's guidance on preventing Legionella (军团菌) suggests keeping heater output at 60 ℃ and hot water at taps at no lower than 50 ℃. Legionella is a bacterium that causes pneumonia. The same guidance also says that preventing Legionella must not increase the risk of children being scalded, and that a thermostatic mixing valve can be fitted at the outlet. If there isn't one, rely on cold first then hot, and test before you put the baby in. Don't walk away while bathing. The American Academy of Pediatrics says more than half of the children who drown in a bathtub are under 1 year old; see §1.12 (keep children in sight near water). Don't carry hot water or soup while holding the baby: the WHO says that in high-income countries the most common scald in infants under 1 year is from a hot drink in a cup. If a scald happens, run cool water over it first; see §13.14 (run cool water after a burn).

Evidence grade

B : Supported by research but without a precise number, or based on small or single studies.

Sources

1. US Consumer Product Safety Commission. Avoiding Tap Water Scalds (Document 5098). https://www.cpsc.gov/s3fs-public/5098.pdf
2. American Academy of Pediatrics (2025). Bathing Your Baby. HealthyChildren.org. https://www.healthychildren.org/English/ages-stages/baby/bathing-skin-care/Pages/Bathing-Your-Newborn.aspx
3. NHS. Washing and bathing your baby（2024-07-23 审阅）. https://www.nhs.uk/baby/caring-for-a-newborn/washing-and-bathing-your-baby/
4. World Health Organization, UNICEF (2008). World report on child injury prevention, Chapter 4 Burns（同一页有中文版《世界预防儿童伤害报告》）. https://iris.who.int/handle/10665/43851
5. Erdmann TC, Feldman KW, Rivara FP, Heimbach DM, Wall HA (1991). Tap water burn prevention: the effect of legislation. Pediatrics, 88(3), 572-577. https://europepmc.org/article/MED/1881739
6. Xu JH, Qiu J, Zhou JH, et al. (2014). Pediatric burns in military hospitals of China from 2001 to 2007: a retrospective study. Burns, 40(8), 1780-1788. https://doi.org/10.1016/j.burns.2014.04.003
7. Zhu L, Zhang Y, Liu L, et al. (2013). Hospitalized pediatric burns in North China: a 10-year epidemiologic review. Burns, 39(5), 1004-1011. https://doi.org/10.1016/j.burns.2012.12.014
8. Han D, Wei Y, Li Y, et al. (2022). Epidemiological and Clinical Characteristics of 5,569 Pediatric Burns in Central China From 2013 to 2019. Frontiers in Public Health, 10, 751615. https://doi.org/10.3389/fpubh.2022.751615
9. World Health Organization (2007). Legionella and the prevention of legionellosis. https://iris.who.int/handle/10665/43233

Translated from the Chinese original. Original book, section 20, tip 17. This section is about health and medicines. It is general information, not a substitute for a doctor’s diagnosis or prescription. Content may be out of date and rules differ by place. When you actually deal with an agency, a doctor or a court, follow what local officials, doctors and lawyers tell you. Disclaimer